Method for spinal stabilization using a rod connector

ABSTRACT

An apparatus is disclosed for connecting first and second elongated spaced apart spinal rods to one another which includes an elongated body portion, a clamp portion depending from the body portion for engaging a spinal rod, the clamp portion defining a deformable clamp body having opposed clamp arms configured for movement between a first position wherein a spinal rod is received between the opposed clamp arms of the clamp body and a second position wherein the spinal rod is securely engaged by the opposed clamp arms the clamp body, and structure operatively associated with the clamp body which is configured to effectuate movement of the opposed clamp arms of the clamp body between the first and second positions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/012,127,filed on Dec. 7, 2001, which is a continuation of Ser. No. 09/535,776,filed Mar. 28, 2000, now abandoned, which claims the benefit of thefiling date of provisional application Ser. No. 60/126,997, filed Mar.30, 1999, the disclosure of which herein is incorporated by reference inits entirety.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The subject disclosure relates to implantable spinal stabilizationsystems for surgical treatment of spinal disorders, and moreparticularly, to an apparatus for connecting cylindrical spinal rods ofa spinal stabilization system to one another across the spinous process.

2. Background of the Related Art

The spinal column is a complex system of bones and connective tissuewhich protects critical elements of the nervous system. Despite thesecomplexities, the spine is a highly flexible structure, capable of ahigh degree of curvature and twist through a wide range of motion.Trauma or developmental irregularities can result is spinal pathologieswhich limit this range of motion.

For many years, orthopedic surgeons have attempted to correct spinalirregularities and restore stability to traumatized areas of the spinethrough immobilization. Over the past ten years, spinal implant systemshave been developed to achieve immobilization. Examples of such systemsare disclosed in U.S. Pat. Nos. 5,102,412 and 5,181,917. Such systemsoften include spinal instrumentation having connective structures suchas elongated rods which are placed on opposite sides of the portion ofthe spinal column intended to be immobilized. Screws and hooks arecommonly utilized to facilitate segmental attachment of such connectivestructures to the posterior surfaces of the spinal laminae, through thepedicles, and into the vertebral bodies.

These components provide the necessary stability both in tension andcompression to achieve immobilization.

It has been found that when a pair of spinal rods are fastened inparallel on either side of the spinous process, the assembly can besignificantly strengthened by using at least one additional rod tohorizontally bridge the pair of spinal rods. An example of a cross braceassembly of this type is disclosed in U.S. Pat. No. 5,084,049. Devicessuch as these commonly consist of a threaded rod for providing thedesired lateral support. The threaded rod is fastened to each of thespinal rods by clamps located on each end thereof. However, thisconfiguration is bulky and can cause irritation of the patient's backmuscles and other tissue which might rub against the device. A crossbrace assembly that overcomes the problems associated with bulkystabilization assemblies by fitting closer to the spine, preferably inthe same general plane as the cylindrical spinal rods, is disclosed incommonly assigned U.S. Pat. No. 5,989,251.

It has also been found that the distance between a pair of spinal rodslocated on either side of the spine can vary depending upon the anatomyof the patient and the manner in which the rods are secured to thespinous process. Thus, transverse rod connectors have been designed withadjustable bridging structures to accommodate this variability, asdisclosed, for example, in U.S. Pat. Nos. 5,752,955 and 5,947,966.

Most existing transverse connectors consist of rods, plates, and barslinked to the longitudinal rods by coupling mechanisms with set screws,nuts, or a combination of each.

These connectors require several components and instruments to build theconstructs. Each additional component or instrument required to assemblethe connectors adds to the complexity of the surgical procedure.Examples of connectors constructed from multiple components aredisclosed in U.S. Pat. Nos. 5,312,405, 5,334,203 and 5,498,263.

It would be beneficial to provide an improved device to transverselyconnect spinal rods of a spinal stabilization system to one anotherwhich utilizes a minimum number of components parts and surgicalinstrumentation, and which has a low-profile so as to fit closely to thespine, and which may be easily adjusted during a spinal stabilizationprocedure.

SUMMARY OF THE DISCLOSURE

The subject disclosure is directed to an apparatus for connecting twoconventional spinal rods of a spinal stabilization system to one anotherin such a manner so as to provide an adjustable low-profile rigidlinkage therebetween. In accordance with a preferred embodiment of thesubject disclosure, the apparatus includes an elongated body portion anda clamp portion depending from the body portion for engaging a spinalrod.

Preferably, the clamp portion defines a deflectable clamp body havingopposed clamp arms configured for movement between a first positionwherein a spinal rod is received between the opposed clamp arms of theclamp body and a second position wherein the spinal rod is securelyengaged by the opposed clamp arms of the clamp body. In addition,structural means are operatively associated with the clamp body toeffectuate the movement of the opposed clamp arms of the clamp bodybetween the first and second positions.

In accordance with one aspect of the disclosure, the structural meansfor moving the opposed clamp arms between the first and second positionscomprises a cam lug configured for reception within a bore formed in theclamp body and adapted for axial rotation within the bore. The cam lughas a generally cylindrical body with camming surfaces formed thereon,and the reception bore is defined at least in part by interior walls. Inoperation, the camming surfaces of the cam lug are adapted andconfigured for bearing against the interior walls of the reception boreupon rotation of the cam lug within the reception bore.

In accordance with another aspect of the subject disclosure, thestructural means for moving the opposed clamp arms between the first andsecond positions comprises an engagement tab projecting outwardly froman exterior surface of the clamp body, and a recess formed within theclamp body spaced from the engagement tab. In operation, the engagementtab is grasped with a tool and pulled outwardly to enlarge a gap betweenthe opposed clamp arms.

In accordance with one aspect of the subject disclosure the elongatedbody portion has a predetermined span length for extending between apair of elongated spinal rods disposed in parallel relationship.Alternatively, the elongated body portion has a span length that isselectively variable for extending between a pair of elongated spinalrods disposed in parallel relationship. Accordingly, the elongated bodyportion includes means for selectively adjusting the length of the bodyportion.

In accordance with one aspect of the subject disclosure, the means forselectively adjusting the length of the body portion includes a firstbody portion having an axial bore defined therein and a second bodyportion having an axial shaft for reception within the axial bore of thefirst body portion, and a locking ring for radially compressing thefirst body portion against the second body portion when the axial shaftis disposed within the axial bore. In accordance with another aspect ofthe subject disclosure, the means for selectively adjusting the lengthof the body portion includes a first body portion having a threaded boredefined therein and a second body portion having an threaded shaft forreception within the threaded bore of the first body portion.

These and other unique features of the apparatus disclosed herein andthe method of installing the same will become more readily apparent fromthe following description of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those having ordinary skill in the art to which the disclosedapparatus appertains will more readily understand how to construct anduse the same, reference may be had to the drawings wherein:

FIG. 1 is a perspective view of a spinal stabilization system forimmobilizing a region of the spinal column which includes variable andfixed length rod connecting apparatus constructed in accordance withpreferred embodiments of the subject disclosure, and a set of bonescrews with linear locking mechanisms;

FIG. 1A a perspective view of another spinal stabilization system forimmobilizing a region of the spinal column which includes a set of bonescrews with top-loading rotatable locking mechanisms;

FIG. 2 is a top plan view of the spinal stabilization system of FIG. 1implanted on the posterior side of the spinal column;

FIG. 3 is a perspective view of the variable length rod connectingapparatus of the subject disclosure with the parts thereof separated forease of illustration;

FIG. 4 is a perspective view of the fixed length rod connectingapparatus of the subject disclosure;

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 1illustrating the clamping portion of the rod connecting apparatus ofFIG. 3 in fastened condition;

FIG. 6 is a perspective view of the cam lug of the subject disclosurewhich facilitates movement of the clamping portion of the rod connectingapparatus of FIGS. 3 and 4 between first and second positions;

FIG. 7 is a top plan view of the cam lug illustrated in FIG. 6 showingthe opposed lateral cam surfaces thereof;

FIG. 8 is a perspective view of the variable length rod connectingapparatus of FIG. 3 prior to installation between a pair of parallel Ispinal rod;

FIG. 9 is a perspective view of the variable length rod connectiveapparatus shown in FIG. 8, with the clamping portions thereof engaged tothe spinal rods in a frictionally engaged condition;

FIG. 10 corresponds to the operative step shown in FIG. 9 andillustrates the relative movement of the arms of the clamping portionbetween an initial position and a frictionally engaged position withrespect to a spinal rod extending therethrough prior to being moved intoa tightly secured position about the periphery of the spinal rod;

FIG. 11 is a perspective view of the variable length rod connectingapparatus shown in FIGS. 7 and 8, with the locking collet moved into alocked position to maintain the length of the connector using a surgicalinstrument;

FIG. 12 is a perspective view of the variable length rod connectingapparatus shown in FIGS. 7 and 8, illustrating the positioning of thecam lugs into the reception areas of the clamping portions;

FIG. 13 is a perspective view of the variable length rod connectingapparatus shown in FIG. 12, illustrating the rotation of the cam lugs tofacilitate movement of the clamping portions into a securely fastenedposition to fixedly connect the apparatus to the spinal rods;

FIG. 14 is a perspective view of another variable length rod connectingapparatus constructed in accordance with a preferred embodiment of thesubject disclosure with the parts thereof separated for ease ofillustration;

FIG. 15 is a perspective view of still another variable length rodconnecting apparatus constructed in accordance with a preferredembodiment of the subject disclosure with the parts thereof separatedfor ease of illustration; and

FIG. 16 is a perspective view of a kit containing various components andtools constructed in accordance with the subject disclosure.

These and other features of the apparatus disclosed herein will becomemore readily apparent to those having ordinary skill in the art from thefollowing detailed description of the invention taken in conjunctionwith the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference numerals identifysimilar structural elements of the subject apparatus, there isillustrated in FIGS. 1 and 2 a spinal stabilization system constructedin accordance with a preferred embodiment of the subject disclosure anddesignated generally by reference numeral 10.

Referring to FIG. 1, spinal stabilization system 10 includes a pair ofelongated spinal rods 12 and 14. The spinal rods are adapted forparallel deployment on either side of the spinous process, asillustrated in FIG. 2. Spinal rods 12 and 14 are of a conventional type,constructed from a bio-compatible material and having a circularcross-section with a smooth outer surface finish. Spinal rods 12 and 14are segmentally secured to the bones of the spinous process by a varietyof structural components including, for example, bone screws 18.

Bone screws 18 have linear locking mechanisms of the type disclosed incommonly assigned U.S. Pat. No. 5,989,251, the disclosure of which isherein incorporated by reference in its entirety. An alternative spinalstabilization system designated generally by reference numeral 10 a isillustrated in FIG. 1A. Spinal stabilization system 10 a includes bonescrews 18 a that have top-loading rotatable locking mechanisms of thetype disclosed in commonly assigned U.S. application Ser. No.09/487,942, the entirety.

It has been found that when a pair of spinal rods are fastened to oneanother in parallel relationship on either side of the spinous process,as illustrated in FIGS. 1 and 2, the stabilization system can besignificantly strengthened. Thus, the spinal rods 12 and 14 ofstabilization system 10 are connected to one another by a plurality ofrod linking devices constructed in accordance with a preferredembodiment of the subject disclosure. FIGS. 1 and 2 illustrate twoembodiments of the rod linking device of the subject disclosureconstructed from high-strength, low-weight, corrosion resistant,bio-compatible metal alloy, such as, for example, titanium or stainlesssteel.

The first embodiment is a variable length rod linking device designatedgenerally by reference numeral 20. (See FIG. 3). The second embodimenthas a fixed length and is designated by reference numeral 60. (See FIG.4). Rod linking device 20 is adapted and configured to be selectivelyadjusted during a spinal stabilization procedure to bridge the gap thatexists between spinal rod 12 and 14. In contrast, rod linking device 60has a predetermined span length and is configured to bridge a fixed gapbetween spinal rods 12 and 14. As discussed in greater detailhereinbelow, rod linking devices 20 and 60, also referred to herein astransverse rod connectors 20 and 60, both have a unique rod engagingsystem in the form of a generally u-shaped deflectable clamping portionor hook.

Referring now to FIG. 3, there is illustrated the variable length rodlinking device 20 of the subject disclosure. Rod connector 20 includesfirst and second body portions 22 and 24. The distal section 22 d of thefirst body portion 22 has a slight outward taper so that the outerdiameter of the distal section 22 d is slightly greater than that of themain section of the first body portion 22. In addition, an axialreception bore 26 is defined in the first body portion 22 for receivingthe second body portion 24. An annular locking collet 28 is operativelyassociated with the first body portion 22 for securely retaining thesecond body portion 24 within the axial reception bore 26. Moreparticularly, the distal section 22 d of the first body portion 22 has apair of diametrically opposed compression slots 30 a and 30 b definedtherein, which extend from the free distal end of body portion 22 to alocation intermediate its length, to facilitate radial compression ofthe distal end section 22 d of body portion 22 against the second bodyportion 24 when it is disposed within axial bore 26.

Annular locking collet 28 is coaxially positioned on body portion 22 andis configured for axial movement along the length thereof, between anannular blocking flange 34 disposed intermediate the length of bodypotion 22 and a pair of diametrically opposed blocking ribs 36 a and 36b disposed at the free distal end of body portion 22. In use, movementof the locking collet 28 between an initial position adjacent annularblocking flange 34 and a final position adjacent blocking ribs 36 a and36 b causes radial compression of the distal end section 22 d of bodyportion 22, as the locking collet 28 moves relative to the outwardlytapered distal section 22 d of body portion 22.

As best seen in FIG. 3, blocking ribs 36 a and 36 b are dimensioned andconfigured to facilitate the mounting of locking collet 28 on bodyportion 22 during assembly of the connector 20. More specifically,during assembly, locking collet 28 is slid over blocking ribs 36 a and36 b for positioning within the area defined between the blocking ribsand annular blocking flange 34. Manipulation of locking collet 28 isaided by the provision of tab 28 a. Also shown in FIG. 3 is a locationguide hole 38 disposed between the free distal end of body portion 22and the annular blocking flange 34. The hole 38 enables a surgeon tolocate the position of the collet 28 during locking to ensure collet 28is moved sufficiently axially to the final locking position.

The second body portion 24 of rod connector 20 is defined by an axialshaft having a uniform outer diameter along substantially the entirelength thereof. The outer diameter of the axial shaft is aboutapproximately equal to the inner diameter of the axial bore 26 definedwithin the first body portion 22, so that an interference fit existstherebetween when the two components are telescopically connected to oneanother during assembly. A retaining ring 24 a is provided to retainfirst and second body portions 24 and 22 together, when assembled, as alip (not shown) on first body portion 22 engages the larger diameterretaining ring 24 a.

With continuing reference to FIG. 3 in conjunction with FIGS. 5 through7, rod connector 20 includes a unique rod engaging system for securelyfastening the transverse connector to spinal rods 12 and 14 during aspinal stabilization procedure with imparting undue stress upon thespine. This system consists of deflectable rod clamps 42 and 44 whichdepends from the first and second body portion 22 and 24, respectively,for securely engaging spinal rods 12 and 14, respectively. Rod clamp 42depending from body portion 22 includes a first and second clamp arms 42a and 42 b between which is defined a gap or channel 43 a foraccommodating spinal rod 12. Similarly, rod clamp 44 which depends frombody portion 24 includes first and second opposed clamp arms 44 a and 44b between which is defined a gap or channel 43 b. Each rod clamp 42, 44has a respective reception port 46, 48 for receiving a camming lug 50.The camming lug 50 is configured to effectuate movement of a clamp 42,44 from an initial position wherein the clamp Is frictionally engagedwith a spinal rod to a final position wherein the clamp is tightlycompressed about the periphery of the spinal rod, as shown in FIG. 5.

Referring to FIGS. 6 and 7, camming lug 50 includes a main body portion52, illustratively generally elliptical in cross section, with enlargedradially outwardly projecting curved lateral camming surfaces 52 a and52 b for interacting with the interior walls of reception ports 46, 48.Camming lug 50 further includes a central aperture 54 for receiving anappropriate tool or implement designed to facilitate axial rotation ofcamming lug 50 within reception ports 46, 48 during a spinalstabilization procedure (see FIG. 13). Advantageously, the rotationalforces imparted upon camming lug 50 during assembly do not impose unduestress on the patient's spine during a stabilization procedure. Aretention flange 56 is provided at the lower end of the main bodyportion 52 of camming lug 50 for cooperating with retention channels 46a, 48 a formed in reception portions 46, 48, respectively. Thisinteraction is intended to inhibit the displacement of the camming lugsfrom the reception ports during shipment, as well as during a surgicalprocedure.

In use, rotation of the camming lug 50 within reception ports 46, 48causes the lateral camming surfaces 52 a, 52 b to bear against the wallsof reception ports 46, 48, urging the walls to expand radiallyoutwardly. In what can best be described as a scissors-like action, theoutward expansion of the port walls causes the clamp arms 42 a, 42 b and44 a, 44 b to move inwardly toward one another so as to reduce the sizeor diameter of the gaps or channels 43 a, 43 b defined therebetween,respectively. As a result, spinal rods 12 and 14 are compressed tightlybetween clamp arms 42 a, 42 b and 44 a, 44 b, as illustrated, forexample, in FIG. 5. It should be recognized that the amount of outwarddeflection of the walls of the reception bore caused by rotating thecanning lugs, and the resultant inward compression of the clamp arms isrelatively small, as the arms must only move a sufficient distance so asto clamp about the spinal rod after having already achieved a frictionalengagement therewith upon initial assembly.

Referring now to FIGS. 8 through 13, there is illustrated, in sequentialorder, one embodiment of the operative steps associated with mountingthe rod linking device 20 of the subject disclosure to a pair ofparallel spinal rods 12 and 14 during a spinal stabilization procedure.As illustrated in FIG. 8, initially the rod linking device 20 is movedinto approximation with spinal rods 12 and 14 with the body portions 22and 24 telescopically mated to one another, i.e., body portion 24 isdisposed within the axial reception bore 26 of body portion 22. At sucha time, locking collet 28 is positioned intermediate the distal endsection 22 of body portion 22, proximal of compression slots 30 a and 30b, and the outwardly tapered portion of the distal section 22 d.

Then, as illustrated in FIG. 9, the rod clamps 42, are brought intoengagement with spinal rods 12 and 14, respectively. At such a time, therod clamps are not securely fastened to the spinal rods and may movedalong the length of the spinal rods or be removed from the rods by thesurgeon for repositioning if such action becomes necessary. FIG. 10illustrates the engagement of a rod clamp with a spinal rod, whereby the“broken lines” illustrate the clamp in a non-engaged position and the“solid lines” illustrate the rod clamp in a frictionally engagedposition.

Referring to FIG. 11, after rod clamps 42 and 44 are engaged to spinalrod 12 and 14, respectively, the length of rod linking device 20 is set.This is accomplished by moving locking collet 28 from its initiallocation adjacent blocking flange 34 toward the blocking ribs 36 a and36 b. This movement is accomplished by an appropriate tool, such assurgical pliers 70 or a similar surgical instrument. As the collect 28translates in the direction of arrow “A”, it moves against the taperedsurfaces of the distal end section 22 d of body portion 22, causing thedistal end section 22 d of body portion 22 to radially compress againstthe cylindrical outer surface of body portion 24 disposed within axialbore 26. When locking collet 28 is moved past location guide hole 38,the user is informed that it is in the locked position.

Referring to FIG. 12, once the appropriate span length of rod linkingdevice 20 has been set, camming lugs 50 are inserted into the receptionports 46 and 48 of deflectable rod clamp 42 and 44. At such a time, thecamming surfaces 50 a and 50 b of the camming lugs are not bearingagainst the walls of the reception ports within which they are disposed.Consequently, the position of the rod clamps can still be adjusted ifsuch action is necessary. It is contemplated in a preferred embodimentthat the system is shipped and utilized with the camming lugs 50 alreadyin reception ports 46 and 48. Thus, in this embodiment, in the stepsshown in FIGS. 8, 9 and 11 the camming lugs would already be in place,saving the surgeon the additional step of inserting the individualcamming lugs 50 in reception ports 46, 48.

Alternatively, it is envisioned that the rod linking devices of thesubject disclosure could be shipped with the camming lugs 50 alreadypositioned within the reception ports 46, 48 so as to reduce the numberof steps required to secure the spinal rods 12, 14 to one another duringa spinal stabilization procedure. Thus, the operative step illustratedin FIG. 12 would become unnecessary.

In either instance, to securely fasten the rod clamps 42, 44 to spinalrods 12, 14, camming lugs 50 are axially rotated in a clock-wisedirection within reception ports 46, 48 using an appropriate surgicaltool or implement, such as for example, lug driver 75. This axialrotation causes the outwardly projecting camming surfaces 52 a, 52 b tobear against the interior walls of the reception ports 46, 48, urgingthem to move radially outwardly. As a result, an equal and oppositescissors-like movement of the opposed clamp arms occurs, causing theopposed clamp arms of each rod clamp 42,44 to tightly engage the outerperiphery of the spinal rods 12, 14, as best seen, for example, in FIG.5, without imparting undue stress on the spine. Once tightly engagedabout the spinal rods, the rod clamps 42, 44 are essentiallyimmobilized.

While the operative steps involved in mounting and securing rod linkingdevice 20 to a pair of spinal rods has been described with respect to asequential order, it will be readily apparent to those having ordinaryskill in the art to which the subject disclosure appertains that theorder or sequence of the operative steps can be altered or modified. Forexample, in an alternative and preferred embodiment, the rod clamps canbe secured to the spinal rods prior to setting the desired length of thelinking device. In this preferred version, the camming lugs 50 arerotated to the clamps 42 and 44 on the spinal rods and then the lockingcollet 28 is moved axially to its final locking position.

Referring to FIG. 4, the rod linking device 60 of the subject disclosurehas a predetermined span length configured to extend a fixed distanceacross the spinous process between a pair of parallel spinal rods 12 and14, as illustrated in FIGS. 1 and 2. Rod linking device 60 includes amain body portion 62 defining a longitudinal axis. Body portion 62 has alow profile construction for fining closely to the spine, so as toreduce any bulkiness associated with spinal stabilization system 10.Deflectable rod clamps 72 and 74 depend from the opposed ends of themain body portion 62 for securely engaging spinal rods 12 and 14,respectively. Rod clamps 72, 74 are substantially identical to rodclamps 42,44 of rod connector 20 and include reception ports 76, 78,respectively for receiving camming lugs 50. As in the previousembodiment, camming lugs 50 are configured to effectuate movement of theopposed clamp arms of rod clamps 72, 74 from an initial position infrictional engagement with the spinal rods to a final position tightlysecured about the periphery of the spinal rods.

Rod linking device 60 is preferably provided in several different spanlengths ranging from about 16 mm in length to about 24 mm in length, inabout 2 mm increments. Additional lengths with varying increments arealso contemplated. Referring to FIG. 16, in accordance with the subjectdisclosure a kit 100 is provided defined by a packing enclosure 110containing, among other things, a plurality of rod linking devices 60a-60 c, each of which has a different preset span length for bridgingthe gap between a pair of elongated spinal rods. For example, the kit100 could include a rod connector 60 a having a span length of about 16mm, a rod connector 60 b having a span length of about 18 mm, and, rodconnector 60 c having a span length of about 20 mm.

Preferably, the rod connectors 60 a-60 c would be packaged with camminglugs 50 already installed in the reception ports of the of clamps ofeach connector. Alternatively, a plurality of camming lugs 50 could beprovided in the package separate from the connectors. The kit would alsoinclude an lug driver 75 for securing the camming lugs 50 within thereception ports of the linking devices. It is envisioned that kit 100could also contain a plurality of variable length rod linking devices 20a-20 c and an appropriate surgical instrument 70 for moving the lockingcollet 28 along the length of the body portion, as described hereinabovewith respect to FIG. 11.

Referring to FIG. 14, there is illustrated another rod linking deviceconstructed in accordance with a preferred embodiment of the subjectdisclosure designated generally by reference number 80. Rod linkingdevice 80 is a variable length connector that includes first and secondtelescopically associated body portions 82 and 84 that are substantiallysimilar to the first and second body portion 22 and 24 of rod linkingdevice 20, which is described hereinabove and illustrated in FIG. 3. Thefirst and second body portions 82, 84 of rod linking device 80 differfrom those of rod linking device 20 in that the rod clamps 92, 94thereof do not employ camming lugs 50 to effectuate movement of theopposed clamp arms 92 a, 92 b and 94 a, 94 b into a tightly engagedposition about the periphery of the spinal rods. Instead, the gaps 93 a,93 b defined between the opposed arms of each rod clamp 92, 94 aredimensioned and configured to tightly engage the periphery of the spinalrods without using a camming lug.

To engage a rod clamp 92, 94 to a spinal rod, the gap 93 a, 93 b betweenthe opposed clamp arms thereof of is radially expanded to allow the rodto enter the gap. This is accomplished by gripping a tab 96, 98projecting outwardly from the leading edge of each rod clamp 92, 94 withan appropriate surgical instrument or tool (not shown), and drawing theouter clamp arm 92 a, 94 a away from the inner clamp arm 92 b, 94 b. Thedeflection of the rod clamp 92, 94 and resultant radial expansion of thegap 93 a, 93 b is aided by the provision of cross-slots 95, 97 formed inrod clamps 92, 94 which provide areas within which the upper portion ofthe outer clamp arms 92 a, 94 a can effectively translate during theradial expansion of the gaps 93 a, 93 b. Once a spinal rod is situatedwithin the gap 93 a, 93 b, the tab 96, 98 is released by the surgeon,allowing the outer clamp arm 92 a, 94 a to return to its normalposition. Thereupon, the inner diameter of the gap 93 a, 93 b issubstantially equal to the outer diameter of the spinal rod and the rodconnector 80 is essentially immobilized.

Referring to FIG. 15, there is illustrated yet another rod linkingdevice constructed in accordance with a preferred embodiment of thesubject disclosure designated generally by reference number 120. Rodlinking device 120 is also a variable length rod connector in that thespan length thereof may be selectively and easily adjusted by a surgeonduring a spinal stabilization procedure to accommodate differentanatomical conditions. Rod linking device 120 includes a first bodyportion 122 which has an internally threaded axial bore 126 extendingtherethrough for receiving a corresponding threaded shaft which definesthe second body portion 124. During assembly, the second body portion124 is threadably secured within the internal bore 126 of the first bodyportion 122 to set the desired span length of rod linking device 120.

The body portions 122 and 124 of rod linking device 120 includedeflectable rod clamps 142 and 144, respectively for securing engagingspinal rods rod during a surgical procedure. In contrast to the rodclamps of rod connectors 20, 60 and 80, described hereinabove, rodclamps 142, 144 do not include additional structures to facilitatemovement of the opposed clamp arms 142 a, 142 b and 144 a, 144 b into asecurely engaged position. Instead, the opposed clamp arms of rod clamps142, 144 are simply snap-fit onto the spinal rods during a surgicalprocedure, so that the opposed clamp arms of the rod clamps are tightlyengaged about the periphery of the spinal rods.

Although the apparatus disclosed herein has been described with respectto preferred embodiments, it is apparent that modifications and changescan be made thereto without departing from the spirit and scope of theinvention as defined by the claims. For example, while each embodimentof the subject rod linking device has been described in conjunction witha particular type of deflectable rod clamping mechanism, it isenvisioned and well within the scope of the subject disclosure that thevarious rod clamping mechanisms disclosed herein are easilyinterchangeable with respect to one another.

1. A method of connecting spinal rods comprising: providing a rodconnector having an elongated body with a first end and a second end,one of said first or second ends having a first deflectable rod clampformed integral with the elongated body, said first clamp having opposedfirst clamp arms capable of moving between a first position and a secondposition and a first cam lug adapted for axial rotation within a firstbore formed in said first clamp; inserting a first spinal rod betweenthe first clamp arms when the first clamp arms are in the firstposition; and rotating the first cam lug within the first bore to imparta force on interior walls of the first bore thereby moving the firstclamp arms of said first clamp to the second position to securely engagethe first spinal rod therebetween.
 2. The method according to claim 1,further comprising the steps of implanting a plurality of pedicle screwsin a plurality of vertebrae and connecting the first spinal rod to thepedicle screws.
 3. The method according to claim 1, wherein theelongated body has a predetermined span length for extending between apair of elongated spinal rods.
 4. The method according to claim 1,further comprising the step of selectively adjusting the length of theelongated body by positioning a first body portion of the elongated bodywith respect to a second body portion of the elongated body.
 5. Themethod according to claim 4, wherein the adjusting step includestelescopically positioning the first body portion with respect to thesecond body portion and locking the first body portion with respect tothe second body portion.
 6. The method according to claim 5, wherein thelocking step includes positioning a locking ring to radially compressthe first body portion against the second body portion.
 7. The methodaccording to claim 4, wherein the adjusting step includes threading athreaded shaft of the second body portion within a threaded bore of thefirst body portion.
 8. The method according to claim 1, wherein theother of said first or second ends of the elongated body includes asecond deflectable rod clamp formed integral with the elongated body,said second clamp having opposed second clamp arms capable of movingbetween a first position and a second position and a second cam lugadapted for axial rotation within a second bore formed in said secondclamp.
 9. The method according to claim 8, further comprising the stepof inserting a second spinal rod between the second clamp arms when thesecond clamp arms are in the first position.
 10. The method according toclaim 9, further comprising the step of rotating the second cam lug toimpart a force on both second clamp arms thereby moving the second clamparms of said second clamp to the second position to securely engage thefirst spinal rod therebetween.
 11. The method according to claim 10,further comprising the steps of implanting a plurality of pedicle screwsin a plurality of vertebrae and connecting the second spinal rod to thepedicle screws.
 12. The method according to claim 10, wherein theelongated body has a predetermined span length for extending between apair of elongated spinal rods.
 13. The method according to claim 10,further comprising the step of selectively adjusting the length of theelongated body by positioning a first body portion of the elongated bodywith respect to a second body portion of the elongated body.
 14. Amethod of connecting spinal rods comprising: providing a rod connectorhaving a first body member including a first clamp formed integraltherewith, the first clamp having arms capable of moving between a rodreceiving position and a rod clamping position, and a second body memberincluding a second clamp formed integral therewith, the second clamphaving arms capable of moving between a rod receiving position and a rodclamping position; engaging a first spinal rod with the first clamp andengaging a second spinal rod with the second clamp; positioning thefirst body member with respect to the second body member based on theposition of the first and second spinal rods with respect to each other;locking a locking collet operatively associated with the first andsecond body members to prevent movement of the first body member withrespect to the second body member; and securing the first and secondclamps to the first and second spinal rods, respectively, the securingstep including rotating a first cam lug adapted for axial rotationwithin a first bore formed in the first clamp, and rotating a second camlug adapted for axial rotation within a second bore formed in the secondclamp, the rotating of the first and second cam lugs imparting a forceon interior walls of the first and second bores thereby causing thefirst and second clamp arms to move to the rod clamping position. 15.The method according to claim 14, wherein the first body member furtherincludes a first end portion defining the first clamp for engaging thefirst spinal rod and a second end portion defining an axial bore with aradially compressible opening, the second body member including a thirdend portion defining the second clamp for engaging the second spinal rodand a fourth end portion defining an axial shaft dimensioned andconfigured for reception within the axial bore of the first body member.16. The method according to claim 15, wherein the locking step includessliding the locking collet between a first position wherein the annularcollet is spaced from the radially compressible opening of the axialbore of the first body member, and a second position wherein the annularcollet surrounds and compresses the radially compressible opening of theaxial bore.
 17. The method according to claim 14, wherein said engagingstep further includes gripping tabs projecting from exterior surfaces ofthe clamps to deflect the clamp arms to the rod receiving position. 18.A method of immobilizing the spine comprising: implanting at least twobone screws in each of a plurality of vertebrae, each vertebrae havingat least one screw on a first side and at least one screw on a secondside; affixing a first spinal rod to the bone screws on the first sideand a second spinal rod to the bone screws on the second side;connecting the first and second spinal rods with a rod connector havingan elongated body portion with opposed ends and rod clamps formedintegral with the elongated body portion and depending from each end,each rod clamp defining a deflectable clamp body having opposed clamparms capable of moving between a first position for receiving the spinalrods and a second position for securely engaging the spinal rods; andallowing the rod connector to remain engaged with the first and secondspinal rods, wherein said connecting step further includes rotating camlugs adapted for axial rotation within bores formed in the clamp bodies,the rotating of each cam lug imparting a force on interior walls of eachbore, respectively, thereby causing the clamp arms to move to the secondposition.
 19. The method according to claim 18, further comprising thestep of selectively adjusting the length of the elongated body bypositioning a first body portion with respect to a second body portion.20. The method according to claim 19, wherein the adjusting stepincludes telescopically positioning the first body portion with respectto the second body portion and locking the first body portion withrespect to the second body portion.
 21. The method according to claim20, wherein the locking step includes positioning a locking ring toradially compress the first body portion against the second bodyportion.